For example, Patent Document 1 disclosed a laser printer as follows. If the time at which a quality improving process, such as a density correcting process, is performed is predetermined, the laser printer executes a density correction at the predetermined time regardless of whether a user uses the laser printer for printing operation.
However, the above described laser printer executes a density correction at the predetermined time regardless of whether the user uses the laser printer for printing operation, and hence, there is a problem in the fact that the user cannot use an image forming apparatus such as a laser printer or inkjet printer during execution of such a density correction.
To solve this problem, Patent Document 2 disclosed an image forming apparatus as follows. If the time at which image formation is started is predetermined, a quality improving process, such as a warm-up process, is started before the predetermined start time (hereinafter, referred to simply as the “set time”).    [Patent Document 1] Japanese Published Unexamined Patent Application No. 2005-119010    [Patent Document 2] Japanese Published Unexamined Patent Application No. 2004-287686